A Decades-Long Quest Reveals New Details of Antimatter

It often goes unmentioned that protons, the positively charged matter particles at the center of atoms, are part antimatter. We learn in school that a proton is a bundle of three elementary particles called quarks—two “up” quarks and a “down” quark, whose electric charges (+2/3 and −1/3, respectively) combine to give the proton its charge […]